var shareToSina = document.querySelectorAll('.share span:last-of-type a:first-of-type');

for (var i = 0; i < shareToSina.length; i++) {
    shareToSina[i].onclick = function() {
        sharetosina();
    }
}

function sharetosina(title, url, picurl) {
    var sharesinastring = 'http://v.t.sina.com.cn/share/share.php?title=' + title + '&url=' + url + '&content=utf-8&sourceUrl=' + url + '&pic=' + picurl;
    window.open(sharesinastring, 'newwindow', 'height=400,width=400,top=100,left=100');
}